The present invention relates to apparatus and methods for removing wedges overlying the windings of a stator core in an electrical machine and particularly relates to apparatus and methods for cutting the wedges longitudinally parallel to the slots to facilitate removal of the wedges and refurbishment of the machine.
In electrical machines such as generators, the stator core has a slot wedging system for retaining the windings in the core. The windings are arranged in circumferentially spaced, longitudinally extending slots, which, along radially inward ends of the slots have dovetail or tapered surfaces. A plurality of wedges typically extend along the length of each circumferentially spaced slot to retain the windings in the slot. The radial outer sides of the wedges are tapered and tapered slides underlie the wedges, forcing the wedges radially inwardly against the dovetail slots. In recent electrical machine construction, ripple springs underlie the slides or wedges and bias the wedges in a radial inward direction. The ripple springs can apply as much as 3500 pounds force to the wedges.
It is common practice to rewedge or rewind the stator core during refurbishment, thus necessitating the removal of the wedges. The wedges are typically removed by sawing them in half in a longitudinal direction. In the past, where ripple springs have not been used, handsaws were used to split the wedges and remove them from the stator core. When biasing the wedges using ripple springs, however, the ripple springs cause the wedge halves to move toward one another as the cut is being made. That is, the action of the ripple spring causes the wedges to bind the cutting blade, causing slippage and tool and core damage as well as generating a potential for injury to the operator. Efforts to remove wedges biased by ripple springs have resulted in labor-intensive, tedious, slow and expensive processes, typically using hand-chisels. Accordingly, there is a need for apparatus and methods for safely, inexpensively and expeditiously removing wedges from a stator core.